1. Field of the Invention
This invention relates to a ring-shaped washer for screws, especially for wood screws, but also for screws for materials used instead of wood such as chipboards, plasterboards and the like. The invention primarily relates to a washer for countersunk screws, but basically it can also be used for other screws such as raised cheese-head screws, roundhead screws or the like. The primary field of application of said washer is in conjunction with a countersunk screw which is designed as a cross-recessed screw in most cases, which is screwed into the materials to be fastened without predrilling. Such screws are on the market for example under the designation of SPAX screws.
2. Prior Art
When fastening construction elements made from wood such as battens or the like the problem often arises that when screwing the screw into the wood, especially when the screw is located close to the end of a batten or the like, the wood is torn due to the wedging effect the countersunk head of the screw exerts on the wooden material when the countersunk screw is screwed in. Moreover, in the case of relatively soft types of wood one can often not avoid in practice that the depth to which the head of the countersunk screw is screwed into the wood, manually or by means of an electric screw driver, varies depending on the force applied. In addition, warped wood and battens can often not be used, as their internal stresses are too great for the wooden material to be forced into the desired position by means of the screw; the wood would tear again, or the head would penetrate too deeply into the wooden material.